Arduino with rotary encoder and 7 segment display
Arduino with rotary encoder and 7 segment display
This topic shows how to connect Arduino UNO with rotary encoder and 7-segment display. Here the rotary encoder is an input device and the 7-segment display is an output device.
The 7-segment display prints the values of the rotary encoder (positive or negative) on 4 digits where the first digit (most left) is used for the minus sign ( -).
To see how to connect Arduino with 7-segment display visit the following post:
Interfacing Arduino with 7-segment display | 4-Digit counter example
To see how the rotary encoder works and how to interface it with Arduino in order to control a DC motor speed, take a look at the project below:
DC Motor control with rotary encoder and Arduino
Parts Required:
- Arduino UNO board —> ATmega328P datasheet
- 4-Digit common anode 7-segment display
- 4 x PNP transistor (2SA1015, 2S9015, 2N3906 …)
- Rotary encoder
- 7 x 100 ohm resistor
- 4 x 4.7k ohm resistor
- Breadboard
- Jumper wires
Arduino with rotary encoder and 7-segment display circuit:
The image below shows example circuit schematic diagram.
The rotary encoder board has 5 pins: GND, + , SW, DT (pin B or data pin) and CLK (pin A or clock pin) where:
GND is connected to Arduino GND pin
+ is connected to Arduino 5V pin
SW is push button pin, not used in this example
DT is connected to Arduino analog pin 5 (A5)
CLK is connected to Arduino analog pin 4 (A4)
The 4 transistors are of the same type (PNP).
Arduino with rotary encoder and 7 segment display code:
The Arduino code below doesn’t use any library for the 7-segment display.
The rotary encoder pin A (CLK) and pin B (DT) are connected to Arduino UNO pins A4 and A5 respectively. Both pins can be used to interrupt the Arduino microcontroller (ATmega328P) whenever there is a change in the state of at least one pin. The following lines are used to enable interrupt-on-change for pins A4 (PCINT12) and A5 (PCINT13):
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// pin change interrupt configuration
PCICR = 2; // enable pin change interrupt for pins PCINT14..8 (Arduino A0 to A5)
PCMSK1 = 0x30; // enable pin change interrupt for pins PCINT12 & PCINT13 (Arduino A4 & A5)
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Since the 4 digits are multiplexed we need to refresh the display very quickly (display one digit at a time, others are off). For that I used Timer1 module interrupt with the following configuration:
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// Timer1 module overflow interrupt configuration
TCCR1A = 0;
TCCR1B = 1; // enable Timer1 with prescaler = 1 ( 16 ticks each 1 µs)
TCNT1 = 0; // set Timer1 preload value to 0 (reset)
TIMSK1 = 1; // enable Timer1 overflow interrupt
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With the above configuration Timer1 module overflows every 4096 microseconds (4096 = 65536/16).
Note that Timer1 module is 16-bit timer, prescaler = 1 (TCCR1B = 1) and Arduino UNO clock = 16MHz.
Full Arduino code:
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/*
* Interfacing Arduino with common anode 7-segment display.
* Print rotary encoder values on 4-digit 7-segment display.
* This is a free software with NO WARRANTY.
* http://simple-circuit.com/
*/
// segment pin definitions
#define SegA 12
#define SegB 11
#define SegC 10
#define SegD 9
#define SegE 8
#define SegF 7
#define SegG 6
// common pins of the four digits definitions
#define Dig1 5
#define Dig2 4
#define Dig3 3
#define Dig4 2
// variable declarations
byte current_digit, last_read;
int8_t quad = 0, change;
int enc_value = 0;
void setup()
{
pinMode(SegA, OUTPUT);
pinMode(SegB, OUTPUT);
pinMode(SegC, OUTPUT);
pinMode(SegD, OUTPUT);
pinMode(SegE, OUTPUT);
pinMode(SegF, OUTPUT);
pinMode(SegG, OUTPUT);
pinMode(Dig1, OUTPUT);
pinMode(Dig2, OUTPUT);
pinMode(Dig3, OUTPUT);
pinMode(Dig4, OUTPUT);
pinMode(A4, INPUT_PULLUP);
pinMode(A5, INPUT_PULLUP);
last_read = digitalRead(A5) << 1 | digitalRead(A4);
disp_off(); // turn off the display
// Timer1 module overflow interrupt configuration
TCCR1A = 0;
TCCR1B = 1; // enable Timer1 with prescaler = 1 ( 16 ticks each 1 µs)
TCNT1 = 0; // set Timer1 preload value to 0 (reset)
TIMSK1 = 1; // enable Timer1 overflow interrupt
// pin change interrupt configuration
PCICR = 2; // enable pin change interrupt for pins PCINT14..8 (Arduino A0 to A5)
PCMSK1 = 0x30; // enable pin change interrupt for pins PCINT12 & PCINT13 (Arduino A4 & A5)
}
ISR(TIMER1_OVF_vect) // Timer1 interrupt service routine (ISR)
{
disp_off(); // turn off the display
uint16_t abs_value = abs(enc_value); // abs: absolute value
switch (current_digit)
{
case 1:
if(enc_value < 0) // if negative value
{ // print minus sign (-) on digit 1 (most left digit)
disp(10); // prepare to display digit 1
digitalWrite(Dig1, LOW); // turn on digit 1
}
break;
case 2:
disp( (abs_value / 100) % 10); // prepare to display digit 2
digitalWrite(Dig2, LOW); // turn on digit 2
break;
case 3:
disp( (abs_value / 10) % 10); // prepare to display digit 3
digitalWrite(Dig3, LOW); // turn on digit 3
break;
case 4:
disp(abs_value % 10); // prepare to display digit 4 (most right)
digitalWrite(Dig4, LOW); // turn on digit 4
}
current_digit = (current_digit % 4) + 1;
}
ISR (PCINT1_vect) // ISR for Arduino A4 (PCINT12) and A5 (PCINT13) pins
{
uint8_t encoderRead = 0;
encoderRead = digitalRead(A5) << 1 | digitalRead(A4);
if(encoderRead == last_read)
return;
if(bitRead(encoderRead, 0) == bitRead(last_read, 1))
quad -= 1;
else
quad += 1;
last_read = encoderRead;
}
int8_t EncoderGet(void)
{
int8_t val = 0;
while(quad >= 4){
val += 1;
quad -= 4;
}
while(quad <= –4){
val -= 1;
quad += 4;
}
return val;
}
// main loop
void loop()
{
change = EncoderGet();
if(change)
enc_value += change;
delay(100); // wait 100 milliseconds
}
void disp(byte number)
{
switch (number)
{
case 0: // print 0
digitalWrite(SegA, LOW);
digitalWrite(SegB, LOW);
digitalWrite(SegC, LOW);
digitalWrite(SegD, LOW);
digitalWrite(SegE, LOW);
digitalWrite(SegF, LOW);
digitalWrite(SegG, HIGH);
break;
case 1: // print 1
digitalWrite(SegA, HIGH);
digitalWrite(SegB, LOW);
digitalWrite(SegC, LOW);
digitalWrite(SegD, HIGH);
digitalWrite(SegE, HIGH);
digitalWrite(SegF, HIGH);
digitalWrite(SegG, HIGH);
break;
case 2: // print 2
digitalWrite(SegA, LOW);
digitalWrite(SegB, LOW);
digitalWrite(SegC, HIGH);
digitalWrite(SegD, LOW);
digitalWrite(SegE, LOW);
digitalWrite(SegF, HIGH);
digitalWrite(SegG, LOW);
break;
case 3: // print 3
digitalWrite(SegA, LOW);
digitalWrite(SegB, LOW);
digitalWrite(SegC, LOW);
digitalWrite(SegD, LOW);
digitalWrite(SegE, HIGH);
digitalWrite(SegF, HIGH);
digitalWrite(SegG, LOW);
break;
case 4: // print 4
digitalWrite(SegA, HIGH);
digitalWrite(SegB, LOW);
digitalWrite(SegC, LOW);
digitalWrite(SegD, HIGH);
digitalWrite(SegE, HIGH);
digitalWrite(SegF, LOW);
digitalWrite(SegG, LOW);
break;
case 5: // print 5
digitalWrite(SegA, LOW);
digitalWrite(SegB, HIGH);
digitalWrite(SegC, LOW);
digitalWrite(SegD, LOW);
digitalWrite(SegE, HIGH);
digitalWrite(SegF, LOW);
digitalWrite(SegG, LOW);
break;
case 6: // print 6
digitalWrite(SegA, LOW);
digitalWrite(SegB, HIGH);
digitalWrite(SegC, LOW);
digitalWrite(SegD, LOW);
digitalWrite(SegE, LOW);
digitalWrite(SegF, LOW);
digitalWrite(SegG, LOW);
break;
case 7: // print 7
digitalWrite(SegA, LOW);
digitalWrite(SegB, LOW);
digitalWrite(SegC, LOW);
digitalWrite(SegD, HIGH);
digitalWrite(SegE, HIGH);
digitalWrite(SegF, HIGH);
digitalWrite(SegG, HIGH);
break;
case 8: // print 8
digitalWrite(SegA, LOW);
digitalWrite(SegB, LOW);
digitalWrite(SegC, LOW);
digitalWrite(SegD, LOW);
digitalWrite(SegE, LOW);
digitalWrite(SegF, LOW);
digitalWrite(SegG, LOW);
break;
case 9: // print 9
digitalWrite(SegA, LOW);
digitalWrite(SegB, LOW);
digitalWrite(SegC, LOW);
digitalWrite(SegD, LOW);
digitalWrite(SegE, HIGH);
digitalWrite(SegF, LOW);
digitalWrite(SegG, LOW);
break;
case 10: // print –
digitalWrite(SegA, HIGH);
digitalWrite(SegB, HIGH);
digitalWrite(SegC, HIGH);
digitalWrite(SegD, HIGH);
digitalWrite(SegE, HIGH);
digitalWrite(SegF, HIGH);
digitalWrite(SegG, LOW);
}
}
void disp_off()
{
digitalWrite(Dig1, HIGH);
digitalWrite(Dig2, HIGH);
digitalWrite(Dig3, HIGH);
digitalWrite(Dig4, HIGH);
}
// end of code.
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The following small video shows a test circuit of this project:
